PROJECT SUMMARY The developmental origins of asthma and lung growth begin in utero. A critical step in identifying lifelong risk is characterizing exposures and mechanisms that lead to and maintain this early predisposition. Our research team has established links between prenatal stress, including maternal lifetime trauma, and child wheeze, asthma, and reduced lung function. We focus on traumatic experiences, which occur more commonly in lower-income, minority women, are especially likely to lead to persistent psychophysiological alterations, and have documented intergenerational effects. However, pathways by which maternal trauma predispose children to respiratory disease are not well delineated. Mechanisms central to the pathophysiology of wheeze/asthma and lung growth and development overlap and involve a cascade of events that include disrupted immune, neuroendocrine and autonomic function as well as oxidative stress. Trauma-related alterations in these key regulatory systems in women may persist into pregnancy and impair development of these same interrelated systems in the fetus, increasing risk for future respiratory disease. The placenta regulates effects of the gestational milieu on the fetus through the release of molecular signals, including microRNAs (miRNAs), small non-coding RNAs that regulate numerous biological processes through epigenetic control of gene expression. Placental trophoblasts actively sort miRNAs into extracellular vesicles (EVs), i.e., 0.05-1?m membrane-bound vesicles released into maternal and fetal circulations. The secretion and content of EV-encapsulated placental miRNAs are influenced by stress-related changes to the in utero milieu. EV-encapsulated miRNAs prime maternal and fetal tissues via messenger RNA (mRNA) silencing that alters gene expression of large gene sets. We leverage an established longitudinal pregnancy cohort study with measures of maternal lifetime trauma, bio-banked maternal mid-pregnancy plasma and venous cord plasma and placental tissue collected at birth, with ongoing respiratory phenotyping (repeated wheeze and lung function indexed by impulse oscillometry (IOS) at age 48 months). We will investigate associations among maternal lifetime trauma, EV- encapsulated placental miRNAs in maternal mid-pregnancy and venous cord plasma, miRNA/mRNA profiles in placenta from normal term births ( ? 37 weeks), and respiratory phenotypes in children. Using a multi-stage approach to discover and replicate placenta-specific miRNAs related to maternal trauma and child outcomes, we may identify pathways associated with intergenerational transmission of maternal trauma and those potentially involved in programming respiratory disease risk in children. Given the evolving understanding of the central role of EVs in pregnancy and tissue signaling, our findings may provide a model that can be extended to additional prenatal risk factors and other fetal disorders.